1. Field of the Invention
The present invention relates to an ATM (Asynchronous Transfer Mode) cell switching system, and in particular to an ATM cell switching system which is implemented using a novel ATM cell switching technique.
2. Description of the Conventional Art
FIG. 1 is a block diagram illustrating a conventional line switching system.
As shown therein, the conventional line switching system includes a plurality of sub-switching systems 10-1 through 10-n for switching local calls, and a main switching system 20 for controlling the whole switching systems and switching a global call among the sub-switching systems 10-1 through 10-n.
The sub-switching system 10-1 through 10-n each include a local CPU (Central Processing Unit) 11 for judging whether a subscriber""s call is a local call or a global call, a local switching unit 12 for switching a local call in accordance with a result of the judgement, and a multiplexor/demultiplexor 13 connected between the local switching unit 12 and a link for multiplexing/demultiplexing the global call.
In addition, the main switching system 20 includes a main CPU 21 for managing all call information and a database, a main switching unit 22 for switching the global call in accordance with a control of the main CPU 21, and multiplexor/demultiplexors 23-1 through 23-n corresponding with the sub-switching systems 10-1 through 10-n.
The local switching unit 12 is formed of a time switch, and the main switching unit 22 is formed of a time switch or a space switch. In addition, the time switch has a switching capacity corresponding to the number of subscribers, and the local and main switching units 12 and 22 are connected through a link.
The call set-up procedure of the conventional line switching system will be explained with reference to FIG. 1.
First, the local call of the sub-switching system 10-1 and the global call between two sub-switching systems 10-1 and 10-2 will be explained.
1. Local Call
When a call generated by a subscriber 1 is inputted into the sub-switching system 10-1 through a PCM (Pulse Code Modulation) highway (hereinafter called as a highway) of 2 Mbps, the local CPU 11 judges whether the call corresponds to a global call between the sub-switching systems or a local call in each sub-switching system. At this time, the call judgement is implemented by detecting a key input, etc. of the subscriber.
As a result of the judgement, if the call is a local call, the local CPU 11 controls a time switch of the local switching unit 12 and outputs a corresponding setup information to the main CPU 21 of the main switching system 20 through a control line 33, so that the main CPU 21 controls the switching state of the sub-switching system 10-1. Therefore, a communication between the subscriber 1 and the subscriber n of the sub-switching system 10-1 is implemented based on a switching operation of the local switching unit 12.
2. Global Call
In addition, as a result of the judgement, the call is a global call between the sub-switching systems 10-1 and 10-2, the local CPU 11 controls the local switching unit 12, and an identification number of the subscriber 1 and an identification number of the subscriber n are informed to the main CPU 21 through the control line 33. Therefore, an audio data of the subscriber 1 switched by the local switching unit 12 is inputted into the multiplexor/demultiplexor 13 through a highway 31, and the multiplexor/demultiplexor 13 multiplexes an audio data and transmits to the main switching system 20 through the link 32.
At this time, the main CPU 21 of the main switching system 20 receives the identification numbers of the subscribers 1 and n inputted through the control line 33 and then recognizes the sub-switching system 10-2 of the subscriber n from the database for thereby controlling the main switching unit 22 and outputting an identification number of the subscriber n to the sub-switching system 10-2 through the control line 33. In addition, the multiplexor/demultiplexor 23-1 demultiplexes the audio data of the subscriber 1 inputted through the link 32 and outputs to the main switching unit 22.
Therefore, the main switching unit 22 switches a corresponding highway 31 in accordance with a control of the main CPU 21, and the audio data of the subscriber 1 demultiplexed by the multiplexor/demultiplexor 23-1 is demultiplexed again by the multiplexor/demultiplexor 23-2 and then is transmitted to the sub-switching system through the link 32.
The local CPU 11 of the sub-switching system 10-2 controls the local switching unit 12 in accordance with an identification information of the subscriber n inputted from the main CPU 21, so that the highway 31 connected with the link 32 and the highway 31 connected with the subscriber are switched through the multiplexor/demultiplexor 13 for thereby forming a communication line (Global call setup), and thus the audio data of the subscriber 1 demultiplexed by the multiplexor/demultiplexor 13 is transferred to the subscriber n. In addition, the local CPU 11 outputs a corresponding Setup completeness information to the main CPU 21 through the control line 33.
Therefore, a communication between the subscriber 1 of the switching system 10-1 and the subscriber n of the sub-switching system 10-2 is implemented through the above-described cell setup procedure. In addition, a local call between the sub-switching systems 10-3 through 10-n and a global call between the sub-switching systems 10-3 through 10-n and the main switching system 20 are implemented in the above-described manner.
However, the conventional line switching system has the following problems.
First, in the conventional line switching system, since a switching speed between the main switching unit and the local switching unit is 2 Mbps, a multimedia service requiring a high speed switching operation is not implemented.
Second, the conventional line switching system has additional control line. In particular, in order to implement a non-blocking line switching operation, the time switches of the main switching system and the sub-switching system should have a predetermined switching capacity corresponding to the number of subscribers. Therefore, the number of switching boards is increased for thereby complicating a system structure and increasing the price.
Third, the conventional line switching system has a plurality of local CPUs for thereby enabling a distributed control structure. However, in the conventional line switching system, since the main CPU manages all call information and a database inputted from the local CPU, the distributed control structure is not fully implemented. As a result, if an error occurs in the main CPU, the whole system may go down for thereby causing inconvenience and degrading the performance of the system.
Fourth, even though the conventional line switching system is capable of processing a large capacity data using a main switching unit, a switching capacity corresponding to the whole number of lines is not implemented due to a high price and limited installation space. As a result, in the case of the global call, since a blocking switch operation is not implemented due to the limited capacity of the switching operation, a traffic may be affected for thereby decreasing a reliability of the system.
Accordingly, it is an object of the present invention to provide an ATM cell switching system which overcomes the aforementioned problems encountered in the conventional art.
It is another object of the present invention to provide an ATM cell switching system which is capable of implementing various multimedia services based on a high speed switching operation by adapting an ATM cell switching technique to a conventional line switching system.
It is still another object of the present invention to provide an ATM cell switching system which is capable of implementing a simple structure and a complete distributed control structure using an ATM cell switching technique.
It is still another object of the present invention to provide an ATM cell switching system which operates irrespective of a traffic by switching global and local calls based on a non-blocking method.
To achieve the above objects, there is provided an ATM cell switching system according to a first embodiment of the present invention which includes more than one node connected between a highway transmitting a subscriber data and a high speed line of an ATM type for implementing a converting operation between the subscriber data and an ATM cell, and an ATM switching unit for receiving an ATM cell from one among the nodes through the high speed link, judging a destination based on a header information and routing the ATM cell to another one among the nodes.
To achieve the above objects, there is provided an ATM cell switching system according to a second embodiment of the present invention which includes a plurality of PCM highways which are a transmission line of TDM type, a plurality of nodes for converting audio data from the PCM highway into an ATM cell or converting the ATM cell into an audio data, a high speed link which is a transmission line of ATM type, and an ATM switching unit connected with a plurality of nodes through the high speed link, respectively, for judging a destination based on a header information of the ATM cell from the nodes and routing a subscriber call.
To achieve the above objects, there is provided an ATM cell switching system according to a third embodiment of the present invention which includes a plurality of PCM highways of a TDM type, a plurality of nodes for switching an audio data from the PCM highway and performing a converting operation between an audio data and an ATM cell, a high speed link of an ATM type, and an ATM switching unit connected with the nodes through the high speed link for routing a subscriber call, said ATM switching unit including a plurality of link interfaces matching with the nodes, and an ATM switch for judging a destination based on a header information of an ATM cell inputted through the link interface unit and routing to the opposite side of the node.
Additional advantages, objects and features of the invention will become more apparent from the description which follows.